A work machine such as an agricultural tractor or a construction tractor may include an internal combustion (IC) engine which provides input power to a transmission, which in turn is coupled with and drives the rear axles through a rear end differential.
The transmissions on tractors are typical manual transmissions that provide several output speeds for a given input speed, each of these several output speeds are typically referred to as a gear, with each speed given a sequentially higher gear number with the slowest speed given the number 1 or called “first gear”, etc. The different gears are provided by a series of transmission gears that are arranged to form a particular gear train that produces a particular speed or gear. The transmission includes multiple gears and shafts, with several gears mounted on each shaft. Not all of the gears are used in each gear train. Different gears are idle while the transmission is operating, depending on the gear selected. Shifting mechanisms axially move along the shaft to selectively alter the series of gears that are engaged to form different gear trains that each produce a particular gear or speed. Also, clutches may be placed in the gear train to idle portions of the shafts and gears.
One type of shifting mechanism is a shift collar. The shift collar is fitted around and rotatably connected to a hub that is rotatably connected to a shaft. A gear spins on the shaft and is fitted beside the collar. The shift collar has features that engage features on the gear when the collar is axially moved toward the gear, causing the gear to rotate with the shaft. When the collar is axially moved away from the gear, the features on the collar are spaced from the gear permitting the gear to spin on the shaft.
The collar may tend to be driven by the forces of the transmission as the collar engages the gear and may move excessively either toward or away from each other and may move out of engagement.
It should be appreciated that, for transmissions with large number of speeds, for example four or more speeds, the number of gears on each shaft and the number of shafts may be quite large. Further, for large tractors having large, powerful engines, the transmission gears must be quite large to transmit the forces generated by such powerful engines. Large numbers of gears and shafts and large sizes of shafts and gears, that are required for the large tractors with transmissions with many speeds, result in heavy, large transmissions. The tractors transport the large, heavy transmissions and may need to work within confined spaces in construction work sites or in agricultural applications. Further, the tractors may need to be transported on public highways.
What is needed in the art is a tractor with a transmission that is more reliable and permits the use of smaller, lighter weight, less expensive components.